This invention relates to a grinder such as for use in grinding meat, and more particularly to features for use with a meat grinder which facilitate removal of hard material such as bone, sinew or gristle so that such materials are not ground along with the meat.
In high volume production of ground meat, it is common for the meat being ground to contain hard materials such as bone, sinew, gristle or the like. It is desirable to remove such material prior to or during grinding of the meat, to ensure that the hard material is not ground along with the meat.
A meat grinder typically includes an orifice plate located at the open end of a tubular housing, and a rotating knife assembly provides a series of knives disposed against a surface of the orifice plate. The knives are mounted to a knife holder, which typically comprises a series of radial arms extending outwardly from a central hub. To remove hard material during grinding, it has been known to provide a series of collection orifices toward the central portion of the orifice plate. With a system of this type, rotation of the knife assembly moves the hard material around the orifice plate, with the hard material eventually making its way toward the center of the orifice plate, where it is received into one of the collection orifices.
A system such as that summarized above generally works satisfactorily to remove hard material from meat during grinding of the meat. However, it has been found that with a lower grade of meat being ground, which contains a greater amount of hard material than higher grade meat, it is nearly impossible for such a system to remove substantially all of the hard material during grinding of the meat.
Accordingly, the present invention has as its object to provide a hard material collection system for use with a meat grinder, which enhances the ability of the grinder to collect hard material during grinding of the meat. It is a further object of the invention to provide a hard material collection system which is used in connection with a conventional grinding system, in which a feed screw advances the meat through a housing toward an orifice plate, and in which a rotating knife assembly is disposed toward the end of the feed screw against the inner surface of the orifice plate. It is further an object of the invention to provide a hard material collection system which is relatively simple in design and in installation, yet which provides a greatly increased ability to collect hard material prior to passing of the hard material through the meat grinding orifices of the orifice plate.
In accordance with one aspect of the invention, a series of spaced collection openings or passages are located toward the center of the orifice plate for collecting hard material such as bone, gristle, sinew or the like. Each collection opening includes a ramped entryway opening onto the surface of the orifice plate facing the knife assembly. The collection openings are relatively large openings, and are located inwardly of relatively small outer openings through which the soft material passes. The ramped entryway to each collection opening extends outwardly toward the outer openings. The collection openings are preferably oval or kidney shaped in plan, and the ramped entryways extend outwardly along one of the long sides of each collection opening. The ramped entryways assist in feeding hard material into the collection openings, and also cooperate with the ends of the collection openings to define shearing edges. When a piece of hard material which is larger than the collection opening is directed into one of the collection openings by the ramped entryway associated therewith, the hard material lodges in the collection opening. Movement of the knife assembly over the collection opening shears off the hard material against the shearing edge defined by the ramped entryway in combination with the end of the collection opening. The portion of the piece of the hard material within the collection opening thereafter passes through the collection opening, and the portion which is sheared off is directed into another collection opening for repeated shearing until it is of a size small enough to pass through a collection opening.
In accordance with another aspect of the invention, the rotating knife assembly includes a central hub and a plurality of knife holding arms extending outwardly from the hub, with a knife mounted to each knife holding arm. The arms are arranged so as to be non-radial relative to the hub, thereby providing non-radial mounting of the knives. This arrangement facilitates movement of the hard material inwardly toward the hub during rotation of the knife assembly. In a preferred embodiment, the hub is provided with a collection pocket forwardly of each knife holding arm for receiving hard material moved inwardly toward the hub during rotation of the knife assembly. The collection pockets on the hub are preferably located in alignment with the collection openings in the orifice plate. The collection openings preferably include ramped entryways as described above for facilitating entry of hard material into the collection openings. Each collection pocket preferably includes an outwardly facing ramped area provided on the hub forwardly of each knife holding arm. In a preferred arrangement, each arm includes a base connected to the hub and an outer end spaced outwardly from the base. The knife holding arms are constructed such that each arm includes a rearwardly facing ramped surface located rearwardly of each knife. The ramped surface of each arm merges with the outwardly facing ramped area of an adjacent one of the collection pockets. The ramped surfaces of the arms define low pressure areas to which hard material migrates upon rotation of the knife assembly. Such material passes through the low pressure areas into the collection pockets, and to the collection passages in the orifice plate. Each arm is arranged so as to provide a positive rake relative to the center of the hub. The longitudinal axis of each arm is preferably tangential to a circle concentric with the center of the hub. In a particularly preferred arrangement, the longitudinal axis of each arm is tangential to a common circle concentric with the center of the hub. In one embodiment, the arms are arranged such that the longitudinal axis of each arm is substantially perpendicular to the longitudinal axes of its adjacent arms.
In accordance with yet another aspect of the invention, the knife holder includes a hub and a plurality of knife holding arms extending outwardly therefrom, with a substantially central passage formed in the hub and adapted to receive a centering shaft therethrough. Each knife holding arm has a forwardly opening knife mounting slot formed therein, with each slot opening into the central passage in the hub. A knife mounting pin extends transversely through each knife mounting slot, and is located toward the outer end of each knife holding arm. Each knife is provided with an outwardly opening pin-receiving slot adapted to receive the knife mounting pin therein, wherein the centering shaft and the knife mounting pins cooperate to maintain the knives in position within the slots. This mounting structure acts to positively retain the knives in the knife holder once the centering shaft is inserted through the central passage formed in the hub.
In accordance with a further aspect of the invention, a collection cup, defining an internal collection cavity, is mounted downstream of the orifice plate for receiving hard material discharged through the orifice plate collection openings. A secondary discharge auger is mounted to and rotatable with the rotating knife assembly, to move the hard material through the collection cavity. A discharge tube is located downstream of the collection cavity, and defines a discharge passage for receiving discharged hard material from the collection cavity. The discharge auger extends into the discharge passage. In a particularly preferred embodiment, the auger has an outside diameter in very close tolerance with the inside wall of the discharge tube which defines the discharge passage. The auger then defines a rotating flow path for moving the hard material downstream through the discharge passage. The discharge passage preferably includes a series of radially spaced axial flutes which open into the discharge passage. Hard material is passed through the flutes upon rotation of the discharge auger. The discharge auger and the discharge tube cooperate to maintain relatively high pressure within the collection cavity, which insures that primarily hard material passes through the orifice plate collection openings and into the collection cavity. The collection cavity preferably includes an axial passage in its downstream end. A set of longitudinally extending flutes are preferably located in the collection cavity axial passage, for assisting in reducing the hard material particles in size and to provide a passage for the hard material particles into the discharge tube. An expansion chamber is preferably disposed between the collection cavity axial passage and the discharge passage, and also downstream of the discharge passage, to assist in moving the hard material through the discharge tube.
In accordance with a further aspect of the invention, a recovery grinding arrangement is provided downstream of the orifice plate. The recovery grinding arrangement recovers and grinds any soft material which may have passed through the collection openings along with the hard material. The recovery grinding arrangement includes a housing having a rotating recovery knife assembly located within its interior. Material passing through the collection openings is routed to the interior of the housing. In one embodiment, a secondary orifice plate is mounted to the end of the housing, and the soft material is forced by the rotating knife assembly through orifices formed therein. The recovered soft material is then mixed with the ground soft material discharged from the primary orifice plate. In another embodiment, a series of orifices are formed in an upper side wall of the housing. The rotating knife assembly forces the recovered soft material upwardly through the orifices, where it mixes with the soft material discharged from the primary orifice plate. In both embodiments, a discharge tube is connected at the outer end of the housing, and includes an internal passage in communication with the interior of the housing. The hard material is routed by the rotating knife assembly to the internal passage of the discharge tube. The secondary discharge auger is connected to the rotating knife assembly, and is disposed within the internal passage of the discharge tube for passing the hard material therethrough. In another embodiment, the recovery grinding arrangement comprises an extended portion of the secondary discharge auger, in combination with an adaptor, which is connected to the collection cup and which receives the inner end of a discharge conduit. The adaptor defines an internal passage having an inside diameter only slightly larger than the outside diameter of the discharge auger, so that the discharge auger defines a rotating flow path for moving hard material through the adaptor passage and into the discharge conduit. The adaptor includes a series of openings along the portion of the adaptor passage within which the discharge auger is located. Any soft material which may be present with the hard material being conveyed through the adaptor passage is squeezed out through the openings formed in the adaptor. The discharged soft material is typically fat, and can either be mixed with the ground product discharged through the orifice plate, or it can be collected for regrinding or for some other use.
In accordance with a further aspect of the invention, a flexible member is located adjacent the outlet of the collection cavity, and is provided with an aperture therethrough for discharging particles of hard material through the aperture from the collection cavity. The secondary discharge auger advances hard material toward the collection cavity outlet. The collection cavity includes a tapered portion defined by structure including one or more inner walls which taper inwardly toward the collection cavity outlet, to define a decreasing transverse dimension to the collection cavity in a direction toward its outlet. An axial passage extends outwardly from the outer end of the tapered portion, and defines the collection cavity outlet. The axial passage is interposed between the collection cavity tapered portion and the flexible member, and the discharge auger extends into the axial passage to force hard material through the axial passage toward the flexible member. The axial passage includes a series of spaced longitudinal flutes through which the hard material passes. A tapered passage is interposed between the collection cavity outlet and the flexible member, to provide a restriction in the flow of hard material toward the flexible member. The tapered passage is defined by a removable insert placed within a sleeve, with the flexible member also being located within the sleeve. A removable mounting arrangement secures the insert and the flexible member within the sleeve. A hard material conduit defines a discharge passage located downstream of the collection cavity outlet, with the flexible member being interposed between the discharge passage and the collection cavity outlet. Particles of hard material are discharged through the flexible member aperture into the discharge passage.
In accordance with a further aspect of the invention, a flow-controlling nozzle is mounted to the end of the discharge conduit, to control the pressure within the collection cavity. The nozzle includes an arrangement for variably controlling the flow rate of hard material through the discharge passage, and thereby the pressure of material therewithin. The nozzle consists of a valve body connected to the end of the discharge conduit and including an internal passage having an inlet end for receiving hard material from the conduit, and an outlet end terminating in a nozzle discharge opening. A movable valve member is mounted to the valve body over the discharge opening. The valve member is movable between an open position and a closed position, and is normally in its closed position. Flow of hard material through the valve body passage toward its outlet end results in engagement of the hard material with the valve member, to move the valve member away from its closed position and to allow the hard material to be discharged through the nozzle discharge opening. The valve member is preferably biased toward its closed position, and is mounted to the valve body by means of an arrangement which provides adjustability in the amount of force required to move the valve member away from its closed position. In one form, the valve body is constructed so as to define a valve seat oriented at an angle to the longitudinal axis of the valve body internal passage, with the nozzle discharge opening being formed in the valve seat. The movable valve member comprises a valve plate engageable with the valve seat so as to normally close the nozzle discharge opening. Adjustability in the biasing of the valve plate toward its closed position is provided by a clamping arrangement which mounts the valve plate to the valve body. The valve plate includes an elongated mounting portion engaged by the clamping arrangement to maintain the valve plate in position relative to the valve body. The clamping arrangement is movable to varying positions on the valve body, such that the degree of resistance provided by the valve plate to flow of hard material through the nozzle discharge opening can be varied. The output of hard material through the nozzle discharge opening is thereby controlled, to control the pressure within the passage defined by the discharge conduit. This aspect of the invention provides a low cost and efficient means to regulate pressure in the hard material discharge passage, and thereby the amount of soft material which is collected along with the hard material, to minimize waste of soft material.
In a particularly preferred embodiment of the invention, the various aspects and features as summarized above are combined into a single structure for facilitating advancing of hard material toward the center of the orifice plate during grinding and passage of the hard material into the collection openings formed in the orifice plate, and for recovering soft material which may pass through the collection openings along with the hard material.
Various other features, advantages and objects of the invention will be made apparent from the following description taken together with the drawings.